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                树上三角形                </h1>
                <p>时间限制：10s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：128MB</p>			</div>
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                                <h3>题目描述</h3><p><div style="text-indent: 24pt"><span style="font-size: medium">给定一大小为n的有点权树，每次询问一对点(u,v)，问是否能在u到v的简单路径上取三个点权，以这三个权值为边长构成一个三角形。同时还支持单点修改。</span></div>
<div><span style="font-size: medium">&nbsp;</span></div>
<p></p></p><hr/><h3>输入格式</h3><p><div style="text-indent: 24pt"><span style="font-size: medium">第一行两个整数n、q表示树的点数和操作数</span></div>
<div style="text-indent: 24pt"><span style="font-size: medium">第二行n个整数表示n个点的点权</span></div>
<div style="text-indent: 24pt"><span style="font-size: medium">以下n-1行，每行2个整数a、b，表示a是b的父亲（以1为根的情况下）</span></div>
<div style="text-indent: 24pt"><span style="font-size: medium">以下q行，每行3个整数t、a、b</span></div>
<div style="text-indent: 44.9pt"><span style="font-size: medium">若t=0，则询问(a,b)</span></div>
<div style="text-indent: 44.9pt"><span style="font-size: medium">若t=1，则将点a的点权修改为b</span></div></p><hr/><h3>输出格式</h3><p><div style="text-indent: 24pt"><span style="font-size: medium">对每个询问输出一行表示答案，&ldquo;Y&rdquo;表示有解，&ldquo;N&rdquo;表示无解。</span></div></p><hr/><h3>样例输入</h3><pre>5 5
1 2 3 4 5
1 2
2 3
3 4
1 5
0 1 3
0 4 5
1 1 4
0 2 5
0 2 3
</pre><hr/><h3>样例输出</h3><pre>N
Y
Y
N
</pre><hr/><h3>提示</h3><p><p>对于100%的数据，n,q&lt;=100000，点权范围[1,231-1]<br />
&nbsp;</p></p><hr/><h3>题目来源</h3><p>没有写明来源</p>
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